36 



ME. ST. GEORGE MIVAET ON THE 



VEETEBE^ OF APTEEYX (twice the natural size). 

 Fig. 33. Fig. 34. 



az ac 



Fig. 35. 



Fig. 33. Dorsal view of third vertebra. 

 Fig. 35. Dorsal view of fifth vertebra. 



Rg. 34. Dorsal view of fourth vertebra. 

 Fig. 36. Dorsal view of sixth vertebra. 



ac, preasial surface of centrum ; az, priczygapopliyses ; d, the diapophjsial element ; kp, the hyperapophysial eletuent ; 

 ns, neural spine ; p.s', postaxial surface of centrum ; pz, postzygapophyses. 



ing the diapophysis with the parapophysis develops a tubercular process on its outer 

 surface, which projects postaxiad and increases the complexity of the skeleton of the 

 neck (fig. 37). The process is in series with that part of each thoracic rib which pro- 

 ceeds distad from the tuberculum. 



In the tenth and eleventh vertebrae (as in A. owenii, but not in A. australis) the cata- 

 pophyses, which have been increasing in conspicuousness and mesiad flexion, from the 

 fourth vertebra, unite together and form a subvertebral ring. 



In the tiuelfth vertebra a median hypapophysial process begins to appear, and the 

 hyperapophyses become more closely approximated to the posterior zygapophyses. 

 These characters are more marked in the thirteenth vertebra, in which vertebra, in A. 

 ovjenii, the hypapophysis attains its maximum of development, though in A. australis 

 it is largest in the vertebrae from the fourteenth to the seventeenth inclusive. 



In the fourteenth vertebra the hyperapophyses and posterior zygapophyses have 

 become completely blended together, so that the former cease to be distinguishable ; 

 and this vertebra is moreover distinguished from all the cervical vertebrae which are 



